1. Field of the Invention
The invention is in the general field of combined processes for preparing alpha-olefins and alumina from a "growth product" comprising substantially tri-C.sub.2 -C.sub.24 alkylaluminum. More specifically, the invention deals with a process for making both alumina and alpha-olefins including a step which calls for the equilibration of alpha-olefins, triethylaluminum, and aluminum trialcoholate (the alcoholate portions having from 4 to 8 carbon atoms).
2. General Background
It is well-known how to prepare triethylaluminum (Al(C.sub.2 H.sub.5).sub.3) from aluminum, (Al) ethylene (C.sub.2 H.sub.4) and hydrogen (H.sub.2). The details of this preparation will be discussed in the detailed description). It is well-known that triethylaluminum (Al(C.sub.2 H.sub.5).sub.3) will react with ethylene (C.sub.2 H.sub.4) to produce an aluminum product in which the alkyl substituents have increased in length by multiples corresponding to the number of moles of ethylene which have been added between the aluminum and the ethyl groups. The resulting product is usually referred to as "growth product". The "growth product" can be used for the production of other useful materials such as high molecular weight alcohols and alpha-olefins (.alpha.-olefins).
The preparation of alpha-olefins from "growth product" is accomplished by a further reaction of growth with ethylene, (this reaction is known as a displacement reaction). This can be done by any of several methods. One preferred method is to conduct the displacement reaction in the presence of a reduction catalyst such as nickel. Conducting the reaction in the presence of a nickel catalyst has the advantage that it can be conducted at low temperatures and pressures and still obtain a resulting high conversion.
The displacement reaction conducted in the presence of nickel has the following disadvantage. During the separation of the high molecular weight olefins from the low molecular weight aluminum trialkyls (Al(R).sub.3) the reaction product tends to undergo reverse displacement and the high molecular weight olefins tend to isomerize and dimerize under the conditions required for distillation.
The use of an aluminum complexing agent is known in the art and is exemplified in U.S. Pat. No. 3,278,262 which employs an alkali metal cyanide-aluminum alkyl complex to produce both olefins and alkanols. In this process after destruction of the aluminum complex hydrolysis is used to produce hydrated alumina. The hydrolysis also converts alkoxides to alkanols.
We have discovered that adding an aluminum tri-C.sub.4 to -C.sub.8 alcoholate (the alcoholate portions having from 4 to 8 carbon atoms per alcoholate group) to the displacement reaction product, prior to fractionation, prevents deleterious side reactions, e.g. reverse displacement and olefin isomerization. We have furthermore eliminated the necessity of using cyanide, which is poisonous, and difficult to dispose of.